The present invention relates to an apparatus and method for performing tests on a sample of body fluid to be analyzed, and more particularly to a spectrophotometer and method for the automatic detection of a reagent strip.
It is useful for various medical diagnostic purposes to utilize a spectrophotometer to analyze samples of body fluid, for example, to determine the color of a person's urine. A conventional spectrophotometer determines the color of a urine sample disposed on a white, non-reactive pad by illuminating the pad and taking a number reflectance readings from the pad, each having a magnitude relating to a different wavelength of visible light. The color of the urine on the pad may then be determined based upon the relative magnitudes of red, green and blue reflectance signals.
Conventional spectrophotometers may be used to perform a number of different urinalysis tests utilizing a reagent strip on which a number of different reagent pads are disposed. Each reagent pad is provided with a different reagent which causes a color change in response to the presence of a certain type of constituent in urine, such as leukocytes (white blood cells) or red blood cells. Such a reagent strip may have ten different types of reagent pads.
In a conventional spectrophotometer, the process of inspecting a reagent strip is performed by dipping the reagent strip in a urine sample, blotting excess urine from the reagent strip, placing the reagent strip at a designated location in the spectrophotometer, and pressing a start button which causes the spectrophotometer to begin automatic processing and inspection of the reagent strip.
U.S. Pat. No. 4,689,202 to Khoja, et al. discloses a reagent test strip reading instrument that has an area in which reagent strips may be placed and a blotter arm 108 that automatically moves reagent strips, one at a time, from the placement area towards an inspection area. As described in column 11 of the Khoja, et al. patent, the automatic movement of the blotter arm 108 is synchronized to the periodic movement of a strip advancing member 116.
In a prior art reagent strip reading instrument marketed by the assignee of this patent under the name "Clinitek 200," which instrument was designed generally in accordance with the disclosure of the Khoja, et al. patent, the blotter arm periodically swept across the area on which reagent strips were placed at a rate of about once every ten seconds, regardless of whether or not a reagent strip was present, and the instrument would generate an audible beep once for every sweep of the blotter arm. If no reagent strips were placed in the placement area after about two minutes, the blotter arm would cease its automatic movement. Thereafter, to again initiate the automatic movement of the blotter arm, the user would have to manually press a start button.